As a video display apparatus for displaying a video image taken by a camera, etc., on a screen, for example, a video display system for transmitting a video signal through a network and displaying a video image on an image display section in a different location is available. Such a video display system using a network is used for a monitor camera system for monitoring the taken video images of target areas intensively at a distant location, etc.
As this kind of video display system, a camera control system for improving operability of each camera and lightening the load on a network is known (refer to patent document 1). In the camera control system, when a button provided on an operation screen is operated, a camera operation unit commands a camera management unit to set the angle previously assigned to the button. The camera management unit prohibits transfer of video data until the specified angle is set, and changes the angel at high speed. Accordingly, camera angle change is speeded up and the load on the network at the time can be decreased.
However, the conventional camera control system described above involves the following problem: The camera operation unit (client PC) suppresses transfer of a video image from the camera during the pan/tilt operation in exchange for operability improvement of pan/tilt of the camera to be operated (to be controlled). Thus, the video image displayed on the screen during the pan/tilt operation becomes intermittent and thus it is difficult to finely adjust pan/tilt of the camera while seeing the displayed video image.
The camera control system described above produces single screen display of displaying only a video image from one camera on a display section; however, there is a demand for enabling the user to visually check a plurality of video images at a glance on multiple screen display in one monitor in a monitor camera system for monitoring intensively at a distant location, etc. Usually, a video display system for displaying multiple screens on a display section involves capability restrictions of the network and the units and thus the frame rate of each screen needs to be decreased to suppress the unit load on the display section. Since the transmission capacity and the processing capability of video data in the whole system are almost determined, moving image display is restricted particularly as the number of screens displayed at a time increases. Also in this case, the video image displayed on the screen during the pan/tilt operation becomes intermittent and it is difficult to finely adjust pan/tilt of the camera as with the single screen display.    Patent document 1: Japanese Patent Laid-Open No. 136246/1998